US soldiers killed by a Jordanian air force sergeant in November attempted to surrender to the gunman before he advanced and killed them, a video from the Jordanian army shows.

The army released the footage on Monday in an apparent attempt to reduce anger within the gunman's tribe, after his imprisonment for life led to protests and claims the state was trying to placate its powerful US ally.

The video from King Faisal airbase at al-Jafr, southern Jordan, has put an end to speculation that Maarik al-Tawaiha's actions in November were the result of a misunderstanding.

The gunman, 39, denied the charges and maintained in court that he heard gunshots and opened fire on a convoy transporting US soldiers, believing the base was under attack.

Other base guards said in court they heard what could have been a pistol shot, but did not open fire as they were unsure of its origin.

The Jordanian authorities initially claimed the convoy had failed to stop at the gate, which they later withdrew.

He was not threatened in any way

- Jordanian army on Tawaiha

In a statement released Monday, the Jordanian army said Tawaiha "did not follow military orders nor did he act in self-defence... he was not threatened in any way".

James R Moriarty, a lawyer and father of one of the dead US soldiers, told the New York Times that the FBI had told him the video was released to defuse protests in Jordan and prevent Tawaiha from being presented as a martyr.

In the video a Jordanian guard can be seen raising the barrier at the gate as the convoy drives slowly in, disproving the claim that the soldiers failed to stop. The vehicles halt when bullets fired by Tawaiha, who is off-camera, can be seen hitting the second vehicle.

After returning fire, the remaining American soldiers dive behind concrete barriers and raise their hands to indicate surrender. The gunman approaches the soldiers and continues to fire with an assault rifle as they try to withdraw.

One of two surviving soldiers appears to be hit as they fire back at their attacker, who is eventually shot himself.

A soldier can be seen waving his hands in the air from behind a barrier (screengrab)

The dead US soldiers, Matthew Lewellen, Kevin McEnroe and James Moriarty, were in the region as part of a covert CIA programme to train Syrian rebels, a detail which neither the US or Jordanian governments initially disclosed.

Tawaiha was convicted on 17 July of "voluntary manslaughter" and "insulting the dignity and reputation of the armed forces and violating military orders".

During the month-long trial, Tawaiha had said he had "no intention of killing anyone" and felt no resentment towards Americans. As he left the court after his sentencing he said: "I have all the respect for the king, but I was doing my job."

The were no indications that Tawaiha had links with extremists or held anti-American views.

The court judged that Tawaiha "fired a full magazine of ammunition... intending to kill them after it was clear to him who they were and that they were American personnel."

Tawaiha was sentenced to hard labour for life, a sentence which usually lasts 20 years, but could stretch to a lifetime, a court official told an AFP correspondent at the court.

The court's decision led to angry protests on the road between al-Jafr and the Iraqi border as members of Tawaiha's Howeitat tribe burned tires and briefly blocked the road.

The influential tribe has pressed for a new trial and leaders have argued that Tawaiha had followed the rules of engagement.

The US and Jordan have long maintained a close military alliance. Jordanian bases host some 2,200 American military personnel and Amman is a member of the US-led coalition fighting Islamic State in neighbouring Iraq and Syria.

In 2015 the US increased overall assistance to Jordan to $1bn annually for the period to 2017.